Adsorption Of Methylamine Research Articles

Methylamine (CH3NH2) dehydrogenase by pristine BN nanotube for H2 storage application: A DFT study

We undertook density functional theory (DFT) computations for inspecting the decomposition and adsorption of methylamine (MLA) onto the surface of a pure boron nitride nano-tube (BNNT). We also obtained the activation energies of viable elementary reactions and the adsorption energies of stable complexes. The most suitable reaction pathway which generated one hydrogen cyanide molecule as well as 4 hydrogen atoms was relatively endothermal. For MLA decomposition, the energy barrier was around 44.6 kcal/mol. Due to the fact that the activation energy for the side reaction which generated NH2 as well as CH3 was somewhat high, reducing the temperature could depress the generation of side products.

Tuning Adsorption of Methylamine and Methanethiol on Twisted-Bilayer Graphene

The influence of a second graphene layer on the adsorption of methanethiol and methylamine is studied using density functional theory. Exploring different adsorption sites, we compare adsorption energies of both molecules on the monolayer, A–B stacked bilayer, and three different twisted-bilayer graphene systems. Results show that both molecules are physisorbed with energies larger than room temperature on determined sites, where methylamine is stronger adsorbed than methanethiol. In A–B stacking, adsorption energies are always smaller than those found in the monolayer. However, at some relative angles between the top and bottom graphene layers, the adsorption energy increases suggesting a molecular-adsorption tuning effect. Although the electronic charge at the interlayer and vacuum regions suffer a rearrangement, there is no charge transfer between molecules and graphene layers. It is expected that these results motivate further studies of molecule adsorption using as additional parameter the relative a...

Adsorption of Methylamine on Amorphous Ice under Interstellar Conditions. A Grand Canonical Monte Carlo Simulation Study.

The adsorption of methylamine at the surface of amorphous ice is studied at various temperatures, ranging from 20 to 200 K, by grand canonical Monte Carlo simulations under conditions that are characteristic to the interstellar medium (ISM). The results are also compared with those obtained earlier on crystalline ( Ih) ice. We found that methylamine has a strong ability of being adsorbed on amorphous ice, involving also multilayer adsorption. The decrease of the temperature leads to a substantial increase of this adsorption ability; thus, considerable adsorption is seen at 20-50 K even at bulk gas phase concentrations that are comparable with that of the ISM. Further, methylamine molecules can also be dissolved in the bulk amorphous ice phase. Both the adsorption capacity of amorphous ice and the strength of the adsorption on it are found to be clearly larger than those corresponding to crystalline ( Ih) ice, due to the molecular scale roughness of the amorphous ice surface as well as to the lack of clear orientational preferences of the water molecules at this surface. Thus, the surface density of the saturated adsorption monolayer is estimated to be 12.6 ± 0.4 μmol/m2, 20% larger than the value of 10.35 μmol/m2, obtained earlier for Ih ice, and at low enough surface coverages the adsorbed methylamine molecules are found to easily form up to three hydrogen bonds with the surface water molecules. The estimated heat of adsorption at infinitely low surface coverage is calculated to be -69 ± 5 kJ/mol, being rather close to the estimated heat of solvation in the bulk amorphous ice phase of -74 ± 7 kJ/mol, indicating that there are at least a few positions at the surface where the adsorbed methylamine molecules experience a bulk-like local environment.

Methylamine as Corrosion Inhibitors for Carbon Steel in Hydrochloric Acid Solutions.

The inhibiting effect of methylamin on the corrosion of carbon steel in 1 M HCl was studied by weight loss,. The results showed that the inhibition efficiency increases with increasing the inhibitor concentration, while it decreases with increasing the temperature. The adsorption of methylamine on the carbon steel surface obeys Temkin adsorption isotherm. Some thermodynamic parameters were calculated and discussed. The results obtained from chemical techniques are in good agreement.

Adsorption of Methylamine at the Surface of Ice. A Grand Canonical Monte Carlo Simulation Study

A series of 41 Monte Carlo simulations are performed in the grand canonical ensemble at 200 K to determine the adsorption isotherm and study in detail the adsorption of methylamine at the surface of Ih ice. The adsorption isotherm exhibits a plateau, corresponding to the saturated adsorption monolayer, in a broad range of chemical potentials and pressures. However, even this part of the adsorption isotherm deviates noticeably from the Langmuir shape. Shortly before condensation of methylamine occurs outer molecular layers also start building up. The remarkable stability of the adsorption monolayer is caused by the interplay of the hydrogen-bonding interaction between the adsorbed methylamine and surface water molecules and the dipolar interaction between neighboring adsorbed methylamines. As a consequence, the adsorbed methylamine molecules exhibit a rich orientational distribution relative to the ice surface, and the adsorption is accompanied by rather large energy change.

Detection and kinetics of methylamine on chitosan film coated quartz crystal microbalance electrode

Chitosan (CHS) coated-quartz crystal microbalance (QCM) electrode was utilized as a sensor for the recognition of methylamine. A homogeneous smooth thin film of CHS coating on the QCM electrode was prepared by the drop casting of CHS solution. The frequency shifts (Δf) of the QCM due to the adsorption of methylamine on the CHS film were measured as a function of concentrations. Calibration curve was plotted which shows a linear relationship of Δf (Hz) versus the methylamine concentrations in the range of 0.5–2.3 mg L−1. In addition to the linearity (R2 = 0.994) and short response time, the sensor shows a high sensitivity, reproducibility and fast reversibility. The kinetics of methylamine adsorption onto CHS film were calculated. Based on the dynamic analysis of adsorption, the association constant of methylamine vapor molecules with CHS films was estimated to be 11386.3 M−1. The diffusion coefficients of various aliphatic amines were calculated and showed that methylamine exhibits the highest diffusion coefficient value compared to dimethylamine and diethylamine.

Methylamine adsorption and decomposition on B12N12 nanocage: A density functional theory study

Density functional theory calculations are performed to investigate the adsorption and decomposition of methylamine (CH3NH2) on the surface of a B12N12 fullerene-like nanocage. Two adsorption types and two reaction channels are identified. It is found that the electrical conductivity of the nanocage can be modified upon the adsorption of CH3NH2. The pathways of CH3NH2 decomposition via bond scission of the CN and NH bonds are examined. The results indicate that NH bond scission is the most favorable pathway on the B12N12 surface. The side reaction that generates CH3 and NH2 fragments is endothermic by 15.6kcal/mol with an energy-barrier height of 81.5kcal/mol. For the CH3NH2 decomposition on the B12N12 surface, the rate-determining step appears to be as the following reaction: CH3NH→CH3N+H.

Adsorption of methylamine on mackinawite (FES) surfaces: A density functional theory study

We have used density functional theory calculations to investigate the interaction between methylamine (CH3NH2) and the dominant surfaces of mackinawite (FeS), where the surface and adsorption properties of mackinawite have been characterized using the DFT-D2 method of Grimme. Our calculations show that while the CH3NH2 molecule only interacts weakly with the most stable FeS(001), it adsorbs relatively strongly on the FeS(011) and FeS(100) surfaces releasing energies of 1.26 eV and 1.51 eV, respectively. Analysis of the nature of the bonding reveals that the CH3NH2 molecule interacts with the mackinawite surfaces through the lone-pair of electrons located on the N atom. The electron density built up in the bonding region between N and Fe is very much what one would expect of covalent type of bonding. We observe no significant adsorption-induced changes of the FeS surface structures, suggesting that amine capping agents would not distort the FeS nanoparticle surfaces required for active heterogeneous catalytic reactions. The vibrational frequencies and the infrared spectra of adsorbed methylamine have been calculated and assignments for vibrational modes are used to propose a kinetic model for the desorption process, yielding a simulated temperature programmed desorption with a relative desorption temperature of <140 K at the FeS(011) surface and <170 K at FeS(100) surface.

Impact of surface steps and oxygen pre-coverage on the adsorption of methylamine on gold

Using density functional theory calculations, we report on the adsorption of methylamine on gold and compare its adsorption to a selection of alkylamines, methanol and methanethiol. On the (111) surface, the amines, thiol and alcohol bind in the ontop site with a preference over hollow and bridge sites of 0.3 eV, 0.2 eV and 0.1 eV for methylamine, methanethiol and methanol, respectively. The effect of steps is considered on the (211) surface of gold and we find that methylamine adsorbs 0.2 eV more strongly in the step ontop site of the surface than on the (111) surface. For oxygen atom pre-coverages of 0.04-0.25 ML on the (111) surface, we find cooperative adsorption of amines and oxygen atoms. The energetic costs of adsorbate tilt from the surface normal and of rotation about the gold-heteroatom bond are compared among the studied surfaces and conditions.

Metastable hydronium ions in UV-irradiated ice

We show that the irradiation of UV light (10-11 eV) onto an ice film produces metastable hydronium (H(3)O(+)) ions in the ice at low temperatures (53-140 K). Evidence of the presence of metastable hydronium ions was obtained by experiments involving adsorption of methylamine onto UV-irradiated ice films and hydrogen-deuterium (H∕D) isotopic exchange reaction. The methylamine adsorption experiments showed that photogenerated H(3)O(+) species transferred a proton to the methylamine arriving at the ice surface, thus producing the methyl ammonium ion, which was detected by low energy sputtering method. The H(3)O(+) species induced the H∕D exchange of water, which was monitored through the detection of water isotopomers on the surface by using the Cs(+) reactive ion scattering method. Thermal and temporal stabilities of H(3)O(+) and its proton migration activity were examined. The lifetime of the hydronium ions in the amorphized ice was greater than 1 h at ∼53 K and decreased to ∼5 min at 140 K. Interestingly, a small portion of hydronium ions survived for an extraordinarily long time in the ice, even at 140 K. The average migration distance of protons released from H(3)O(+) in the ice was estimated to be about two water molecules at ∼54 K and about six molecules at 100 K. These results indicate that UV-generated hydronium ions can be efficiently stabilized in low-temperature ice. Such metastable hydronium ions may play a significant role in the acid-base chemistry of ice particles in interstellar clouds.

Ligand-Induced Structural Evolution of Pt55 Nanoparticles: Amine versus Thiol

We report the geometric and electronic effects of amine (with one lone pair electron) and thiol (with two lone pair electrons) ligands on the structural transformation of Pt(55) nanoparticles (NPs) by first-principles calculation. Although a cuboctahedral (COh) structure is less stable than an icosahedral (Ih) structure by 1.36 eV for a bare Pt(55) NP, the activation barrier from the COh to the Ih structure is very high, by 1.97 eV, indicating that it would be difficult to observe the structural evolution of a COh structure to an Ih structure for a bare Pt(55) NP at ambient temperature. However, with the help of the adsorption of methylamine, the structural evolution from a COh structure to an Ih structure is accomplished by the Mackay transformation. This transformation is driven by a combination of both the external forces resulting from the adsorption of the ligand, which pull out the Pt atoms on the face sites of NPs in a radial direction, and the contraction forces in a tangential direction. As more methylamine is added, the Ih structure is observed to return to the original COh structure owing to the directional orbital hybridization that occurs between the Pt NPs and the methylamine. In contrast, such structural evolutions are not observed in the case of methylthiol because the sulfur (S) in the ligand has two lone pair electrons, leading to two Pt-S bonds. As a result, the radial-directed external force that the NPs experience because of the adsorption of methylthiols is much lower than that found in methylamine-ligated NPs. Furthermore, the adsorption of methylthiol leads to an expansion (not contraction) in the tangential direction, which does not qualify as a Mackay transformation. Thus, the Pt NPs ligated with methylthiol do not have a driving force strong enough to cause structural change. The methylthiol-stabilized Pt NPs retain their initial COh structure despite an abundance of ligand adsorption. From these results, we suggest that the NP structure can be controlled by varying the amount and species of ligands.

Adsorption of methylamine on Ni3Al(111) and NiAl(110)—a high resolution photoelectron spectroscopy and density functional theorystudy

Methylamine adsorption on the orderedNi3Al(111) and NiAl(110) surfaces has been investigated by high resolution photoelectron spectroscopyand density functional theory calculations. Methylamine adsorbs molecularly at bothsurfaces at low temperature (90 K). The experiments show that methylamine interacts withthe surface aluminium atoms on both surfaces, resulting in a positive bindingenergy shift relative to the Al 2p bulk contributions. A shift towards lower bindingenergy is also observed on NiAl(110) attributed to first and second layer surfaceAl atoms not bonded to methylamine. According to total energy calculationsmethylamine binds through its N atom to Al on-top sites on NiAl(110) whilethe Ni on-top site is found to be slightly preferred over the Al on-top site onNi3Al(111). Calculated adsorbate induced shifts are, however, in good agreement with theexperimental values only when methylamine is situated in the Al on-top site on bothsurfaces. In both cases, a lone pair bonding mechanism is found.

Exceptionally Strong Hydrogen Bonds Affect the Surface Energy of Colloidal Nanocrystals: Methylamine and Water Adsorption on PbS

First-principles calculations for colloidal PbS nanocrystals reveal a sizable dependence of surface energy on the solution environment. In vacuum, the bare (100) surface is more stable than the bare (111) surface. Methylamine adsorption, however, preferentially lowers the energy of the unreconstructed (111), but the lowering is insufficient to reverse the energy order. Methylamine coadsorption with water can make the (111) surface most stable. The energy lowering is explained in terms of an exceptionally strong hydrogen bonding at the solution-solid interface.

Interactions of Organic Molecules with Calcite and Magnesite Surfaces

This paper presents molecular dynamics simulations of methanoic acid and methylamine molecules interacting with various calcite and magnesite surfaces in aqueous conditions. A new set of potentials for the interaction of nitrogen atoms with mineral surfaces is fitted and tested using ab initio methods. The results show that methanoic acid adsorption is stronger than methylamine adsorption onto calcite and magnesite surfaces. The competition between the surface water structure and the adsorbing molecule is shown to be a major component of the adsorption energy and explains why adsorption is stronger at particular surface indices and onto calcite surfaces rather than magnesite surfaces.

First principles calculations of methylamine and methanol adsorption on hydroxylated quartz (0 0 0 1)

Density functional theory calculations have been used to study the adsorption of methylamine and methanol on the hydroxylated (0 0 0 1) surface of α-quartz. The surface structure for these calculations was based on the structure reported recently by Goumans et al. [T.P.M. Goumans, A. Wander, W.A. Brown, C.R.A. Catlow, Phys. Chem. Chem. Phys. 9 (2007) 2146]. Adsorption of methylamine or methanol in their most energetically preferred sites occurs by breaking one of the hydrogen bonds that exists on the bare surface and creating two hydrogen bonds between the surface and the adsorbed molecule. We report the adsorption energy and the vibrational frequencies associated with adsorption of these two species. Understanding the adsorption of these species on α-quartz (0 0 0 1) will be useful in future consideration of the adsorption of chiral molecules such as amino acids on this surface, which is intrinsically chiral.

The Leading Role of Association in Framework Modification of Highly Siliceous Zeolites with Adsorbed Methylamine

Affinity index (AT value), adsorption heat, X-ray diffraction (XRD), and 13C and 29Si magic-angle spinning (MAS) NMR, FTIR, and Raman spectroscopies were used to study the interaction of highly siliceous MFI-, FAU-, and FER-type zeolites with adsorbed methylamine (MA). Compared with the data for methanol, the much higher AT values and adsorption heats, and significant changes in XRD patterns, 29Si MAS NMR spectra, and FTIR spectra for the zeolites after adsorption of MA, revealed a strong hydrogen-bonding interaction between the perfect framework of the zeolites and the adsorbed MAs. This interaction results from the fact that the H atom of the amine group attacks the [Si-O] framework to form a Si-OHN bond, which leads to the appearance of Si-N bonds in the zeolites at 323 K. Therefore, the zeolite framework can be modified with MA under mild conditions. The highly siliceous MFI zeolite and the H-ZSM-5 zeolite with SiO2/Al2O3=31:1 were modified with MA and investigated by temperature-programmed desorption of CO2. The modified zeolites exhibited greatly enhanced basic properties in comparison with those of the raw materials. The influence of defects in the zeolite on the adsorption and the interaction with MA is discussed.

Adsorption of methylamine at a polycrystalline gold/solution interface

Adsorptive behaviour of the methylamine molecules has been investigated by measuring changes in the differential capacitance of the double layer at the gold/solution interface by the tensammetric method. The differences in adsorption parameters at Θ < 0.8 and >0.8 have been explained by changes in arrangement of the adsorbate.

First Principles Computational Study for Understanding the Interactions between ssDNA and Gold Nanoparticles: Adsorption of Methylamine on Gold Nanoparticulate Surfaces

We conducted a computational adsorption study of methylamine on various surface models of a gold nanoparticle which is facetted by multiple [111] and [100] planes. In addition to these flat surfaces, our models include the stepped surfaces (ridges) formed along the intersections of these planes. Binding on the flat surfaces was fairly weak, but substantially stronger on the ridges by an average of 4.4 kcal/mol. This finding supports the idea that ssDNA's interaction with gold nanoparticles occurs through the amines on the purine/pyrimidine rings. Also, this typically undesirable interaction between DNA and gold nanoparticles is expected to increase as the particle size decreases. Our analysis suggests that particle size is an important controlling parameter to reduce this interaction.

Competitive Adsorption on Wollastonite: An Atomistic Simulation Approach

Atomistic simulation techniques are used to simulate surface structure and adsorption behavior of scarcely floatable wollastonite mineral in the presence of molecular and dissociated water, methanoic acid, and methylamine. The latter two additives represent the two widely used collector head-group molecules. The static energy minimization code METADISE was used to perform the simulation to obtain pure surface energy and adsorption energy in the presence of added molecule. The hydroxylation was performed on those surfaces where low-coordinated silicon was made to saturate by bonding with hydroxyl group, and the subsequent charge neutralization was maintained by adding proton on single-coordinated surface oxygen. A comparison of surface energies revealed that all the surfaces become stabilized in the presence of added molecules; however, the presence of methylamine decreased the surface energy to lower values. Adsorption of dissociated water is preferred by the {100} and {102} surfaces, whereas the {001} surface preferred methylamine adsorption, because these show highly negative adsorption energies. In terms of molecular adsorption, the preferred adsorption sequence for all the surfaces is methylamine > methanoic acid > water without considering coadsorption. For the {100} and {102} surfaces, the adsorption energy values of carboxylic acid and amine are more negative than that of water and therefore we conclude that both carboxyl and amine head-group molecules adsorb preferably on wollastonite. Our simulation verify usability of carboxylic acid head group as widely used collectors for wollastonite flotation and, at the same time, it predicts the use of amine head-group collectors as possible modifiers, which corresponds well with our experimental findings.

Interaction of Methylamine with Highly Siliceous MFI, FAU and FER‐type Zeolites

AbstractThe adsorption of methylamine on highly siliceous MFI, FAU and FER‐type zeolites was investigated with XRD, FT‐IR, Raman, 13C and 29Si MAS NMR, and compared with the adsorption of methanol. As the adsorption of the amine, the relative intensity of XRD peaks of the zeolites has been changed significantly, the high‐resolution 29Si MAS NMR peaks have been broadened and shifted to low field, and the resonance of SiOH groups has appeared. The vibration of NH has been shifted to low frequency and CN vibration moved to high frequency in the IR spectra, and the 13C resonance peak broadened and shifted to high field for the adsorbed amine. The facts reveal an associating interaction between the perfect framework of the zeolites and the adsorbed methylamine with hydrogen bonds, leading to the formation of SiOH groups and the high desorption temperature of the methyl‐amine from the zeolites.